The field of this invention is hydroponic gardening.
Hydroponic gardening relates to the growth of plants for aesthetic appeal and/or for food production without the use of soil. Hydroponic gardening probably first became a reality around 1940 when the U.S. Army utilized hydroponic gardening techniques to grow fresh vegetables in the Pacific Islands. However, there are even earlier patents to hydroponic gardening. U.S. Pat. Nos. 2,241,699 issued to Cooper and 2,188,875 issued to Ellis are examples of very early attempts to utilize hydroponic theories in a practical unit.
There are basically two types of hydroponic systems: an open system and a closed system. In the open hydroponic system, a nutrient solution is periodically fed to the plants as supported in an inorganic medium. The nutrient solution is drained through the inorganic medium to the environment. In the closed hydroponic system, the nutrient solution periodically fed to the plant supported in an inorganic medium is collected and recirculated for further use in later periodic feeding cycles. "Hydroponics -- Toward Perfect Gardening", Houston Home and Garden, September, 1975, pp. 63-69.
Recently, the interest in hydroponic gardening has substantially increased. The reasons for this are probably several and very important. First of all, some of the major countries of the world continue to have problems producing food under typical conditions -- either because of poor weather or poor soil or both. Secondly, in very populated areas such as the United States, the availability of land for gardens for the average homeowner is rapidly decreasing. Hydroponic gardening techniques offer the possibility of home grown food products to the townhouse apartment owner, or the owner of a small home on a small tract who cannot otherwise have a garden. Adding fuel to the burgeoning need for hydroponic gardening is the rising cost of food products.
There are presently various patents in addition to the two already mentioned that disclosed hydroponic gardening systems. For example, U.S. Pat. Nos. 2,952,096, 2,983,076, 3,323,253 and 3,451,162 are directed to closed systems. The previously mentioned patent to Ellis '875 discloses a central plant propagating compartment having mounted above it a trough for distributing nutrients and having mounted below it and at one side a nutrient solution pump. The Ellis patent device includes a rubber bulb connected to tubes which extend from the nutrient solution sump to the nutrient solution trough for the purpose of recirculating the nutrient solution. Thus the Ellis system is a closed system because the nutrient solution is circulated in order to make periodic feedings. The Cooper patent '699 also discloses a hydroponic unit which is a form of a closed system wherein the nutrient solution is fed from a lower compartment into the upper, plant supporting compartment for the purposes of feeding the plants. The nutrient then drains back downwardly into the lower compartment for re-use. The device disclosed in Cooper cannot be converted into an open system.